Every May, the same complaints return: the house is unbearably hot, the AC runs all day, the electricity bills are crushing, the west-facing rooms are unusable. These are not Acts of God. They are consequences of design decisions—decisions that were made, or not made, when the building was planned. This note explains why most homes in Gujarat overheat and how architectural design can fix it—not by adding more technology, but by getting the fundamentals right.

If you ask a homeowner why their house is hot, they will usually blame the weather, the AC unit, or the construction quality. Rarely do they blame the design.

But design is almost always the root cause.

A house that overheats in Gujarat’s summer is usually a house where orientation was ignored, where shading was insufficient, where thermal mass was misused, or where the building envelope was designed for appearance rather than performance.

What actually causes a house to overheat?

Overheating happens when heat enters faster than it can be removed. In a building, heat enters through four main paths:

Solar radiation through windows. Sunlight passing through glass becomes heat inside the building. West-facing windows are the worst offenders because they receive afternoon sun when the day is already hot.

Conduction through walls and roof. Hot external surfaces transfer heat inward. Roofs are the biggest culprits—they receive direct sun all day and can reach 60–70°C in summer.

Infiltration of hot air. Gaps, cracks, and intentional openings allow hot outside air to enter, especially when the building is depressurised by exhaust fans.

Internal heat gains. Appliances, lights, and occupants generate heat. In a poorly designed building, this adds to the cooling load.

Of these, solar radiation through windows and conduction through the roof are usually dominant in Gujarat homes. Fix these, and you fix most of the problem.

Why do modern homes often perform worse than older ones?

This seems counterintuitive. Modern homes have better materials, better glass, better AC systems. Yet many older homes—with thick walls, small windows, and no air-conditioning—stay cooler.

The reason is design priorities. Older homes were designed before air-conditioning was affordable. They had to work with climate, using strategies that have been largely abandoned: thick masonry walls that store coolness, small windows with deep reveals, verandahs and courtyards that provide shade, and room arrangements that put service spaces on hot sides.

Modern homes are often designed for appearance: large windows for views, thin walls for floor area, minimal overhangs for clean lines. They assume AC will solve the comfort problem.

But AC cannot solve a design problem. It can only mask it—at considerable cost.

What design decisions cause the most overheating?

West-facing glass. This is the single biggest cause of overheating in Gujarat homes. A west-facing glass wall or large window will turn the room into an oven every summer afternoon. No curtain, no film, no high-performance glass can fully compensate.

Unshaded windows on any orientation. Even east and south windows need external shading. Without it, direct sun enters the room and heats everything it touches.

Uninsulated or poorly designed roofs. A concrete slab roof with no insulation and no shading will transfer enormous heat into the rooms below. Top-floor apartments and top-floor bedrooms are notorious for overheating.

Lack of thermal mass in the right places. Lightweight construction responds quickly to temperature changes—hot in the day, cold at night. Heavy walls, if shaded, can moderate these swings.

Poor cross-ventilation design. In cooler months, natural ventilation can provide comfort without AC. Homes designed without considering airflow miss this opportunity.

How does architectural design fix overheating—without depending on AC?

This connects to Issue 16 and Issue 17: the solutions are passive strategies embedded in the design, not active systems added later.

Right orientation from the start. Place living spaces on north and east, service spaces on west and south. Minimise west-facing openings. This costs nothing—it only requires thinking about the sun before drawing the plan.

External shading on all openings. Deep chajjas, vertical fins, screens, pergolas, or vegetation—whatever suits the orientation. The goal is to block direct sun before it reaches the glass.

Roof treatment. Insulation, reflective coatings, double roofs, or shaded terraces can reduce roof heat gain by 30–50%. This is one of the highest-impact interventions for top-floor comfort.

Appropriate wall construction. Heavy walls with shading use thermal mass beneficially. Lightweight walls need insulation. The choice depends on the specific design, but it must be a conscious choice.

Cross-ventilation for swing seasons. In Ahmedabad, March–April and September–November can be comfortable without AC if the building allows airflow. Operable windows, stack ventilation, and ceiling fans extend the comfortable months.

What about existing homes that already overheat?

Retrofitting an overheating home is harder than designing correctly from the start, but improvements are possible.

External shading can often be added: bamboo screens, fabric awnings, or metal louvers outside west and south windows make a measurable difference.

Roof treatment—adding insulation above the slab, applying a cool roof coating, or installing a shaded pergola—can dramatically improve top-floor comfort.

Window films and high-performance glass replacements help, but they are less effective than external shading.

Improving night ventilation—opening the house in the evening to flush out heat—can cool thermal mass for the next day.

These are partial fixes. They cannot fully compensate for fundamental design errors. But they can make an uncomfortable home liveable.

What should homeowners ask their architect before design begins?

Ask: How will you handle the west side of this plot? What shading strategy will protect the windows? How will the roof be treated for heat? Can you show me a shadow study for summer afternoons?

If the architect cannot answer these questions with specifics, the design may prioritise appearance over performance.

The deeper point: overheating is a design failure, not a climate inevitability

Gujarat’s climate is demanding, but it is not impossible. Buildings have stayed cool here for centuries—using orientation, shading, mass, and ventilation. The techniques are known.

The homes that overheat are not victims of climate. They are victims of design decisions that ignored climate.

At VNA, we believe every home in Gujarat can be comfortable without excessive air-conditioning—if the design respects the sun. That is the starting point, not an afterthought.

In the next note, I’ll shift from design intent to design evidence: what buildings actually teach architects after occupation, and why post-occupancy evidence matters more than projected performance.

— Ar. Brijesh Patel

Founder & Principal Architect, VastuNirman Architects (VNA)